A blast furnace is typically filled by passing a filler material through an upper opening, or inlet, of the blast furnace. The filler material generally comes from one or more supply tanks placed above, and thus upstream of, the upper opening of the blast furnace.
In order to achieve a good delivery of the material in the blast furnace, the use of a delivery device is known, said delivery device being arranged between the blast furnace inlet and the supply tank outlet. The delivery device is provided with a central supply channel and with a chute arranged downstream of said channel to discharge the filler material. The chute is arranged at the inlet of the blast furnace and can be rotated and tilted during the transition of the filler material.
Document US20120148373 describes a delivery device provided with one or more hydraulic cylinders and with one or more electric motors which are used to tilt and rotate the chute, respectively. The delivery device, defining a longitudinal axis, includes, inside a housing:
an outer ring, which is coaxial to said longitudinal axis, capable of performing a vertical translational movement by means of the hydraulic cylinders;
an inner ring, which is coaxial to said longitudinal axis, coupled to the outer ring by means of a bearing which is designed to allow the inner ring to perform both a vertical translational movement and a rotation movement about the longitudinal axis;
a mechanism coupled to the inner ring and to the chute;
a trunnion, which is coaxial to said longitudinal axis, coupled to the chute and, by means of a toothed bearing, to the pinion of the rotating electric motor.
The chute is tilted by actuating the hydraulic cylinders which move a rod connected to the outer ring which, when vertically translated, generates in turn a vertical translational motion of the inner ring. The mechanism provides for converting the vertical translational motion of the inner ring into a tilting movement of the chute.
The chute rotates by actuating the electric motors, the motion output pinions of which rotate the toothed bearing. The trunnion is fixed to the toothed bearing, whereby the rotation of the chute is achieved.
A disadvantage of such a delivery device is the arrangement of some of its components.
Indeed, from the periphery of the device to the central supply channel for supplying the filler material, the following components are arranged in sequence: the outer ring; the coupling bearing for the coupling between the outer ring and the inner ring; the inner ring; the hydraulic cylinder and the rod connected thereto, which is at about the same radial distance, with respect to the device axis, as the pinion of the rotating electric motor; the toothed bearing which is at about the same radial distance as the trunnion.
In particular (see FIGS. 6 and 7 of US20120148373), the hydraulic cylinders and electric motors are in an innermost position with respect to the coupling bearing between the outer ring and the inner ring. Moreover, the toothed bearing, which is used to transmit the rotation to the chute, is in an innermost position, having a smaller diameter, with respect to the aforesaid coupling bearing.
Disadvantageously, the position of the hydraulic cylinders and electric motors is at about a half of the radius of the peripheral wall of the housing of the delivery device with respect to the central longitudinal axis. The fact that the rods connected to the respective hydraulic cylinders and the pinion of the electric motor are in a radial position deeply inside the delivery device causes a strong stress acting on the bearings, and in particular on the toothed bearings which transmit the rotation motion. This is mainly because the center of gravity of the delivery device moves from the center of the device itself, when the chute is tilted in a substantially vertical position, to a position outside the circumference defined by the toothed bearing when the chute is tilted towards a horizontal position. The stress is particularly detrimental also because the movement of the center of gravity outside said circumference causes a stress of the bearings, which stress is not homogeneously distributed thereon.
Moreover, the size of the hydraulic cylinders and rotating electric motors, which occupy a considerable space inside the delivery device, does not allow large diameter bearings to be used, the performance of which would be better, and does not allow an optimal cooling.
A further disadvantage is that the pinion of the rotating motor directly acts on the toothed bearing, thus stressing it and contributing to its wear.
Yet another disadvantage is represented by the fastening system of the chute, which may be detached from the delivery device and/or generate detrimental vibrations for the bearings and transmission members during its movement.
The thermal insulation cooperating with the cooling system of the delivery device also achieves limited results.
Therefore, a need to provide a device for delivering filler material into a blast furnace which allows to overcome the aforesaid drawbacks is felt.